2011
NATIONAL ELECTRICAL CODE®
STYLE MANUAL
1
FOREWORD
April 1999
The National Electrical Code is used nationally and internationally as the basis for
safeguarding persons, buildings, and their contents from hazards arising from the use of
electricity. It is vitally important that the text be as explicit as possible and that
maximum consistency be achieved in the language used in the text. The Code contains
those provisions considered necessary for safety and thus is widely used as a basis for
legal enforcement in the installation of electrical conductors and equipment in buildings
and certain other premises (as detailed in the Code itself); this places a major
responsibility on those involved in the preparation of the document to use forms of
expression that promote uniform interpretation.
The Technical Correlating Committee of the National Electrical Code Committee has
recognized these responsibilities and has issued this manual.
Preparation and Date of Adoption. This manual was originally prepared by the
Editorial Task Group of the National Electrical Code Committee and adopted by the
National Electrical Code Technical Correlating Committee on May 13, 1969. It was
amended September 22, 1975, October 11, 1984, October 12, 1989, and May 9, 1994.
In January 1999, the Technical Correlating Committee Task Group on the Usability of
the NEC rewrote the manual. It was adopted by the Technical Correlating Committee on
March 19, 1999 and by the Standards Council on April 15, 1999. It was amended March
1, 2001, January 15, 2003, and August 9, 2011
Valuable guidance in the preparation of this manual was provided by several members of
the Technical Correlating Committee.
2
TABLE OF CONTENTS
Foreword
2
Chapter 1 General
1.1 Purpose
1.2 Scope
1.3 Regulatory Adoption
1.4 Examples
4
4
4
4
4
Chapter 2 Document Structure and Numbering
2.1 Subdivisions of the NEC
2.2 Content of NEC Subdivisions.............................................
2.3 Tables and Figures...............................................................
2.4 Numbering Practices............................................................
2.5 General References to Other Articles ...................................
2.6 Exceptions
5
5
8
9
10
11
12
Chapter 3 Editorial Guidelines
3.1 Mandatory Rules, Permissive Rules, and Explanatory
Information
3.2 Word Choices
3.3 Writing Style
13
Chapter 4 References and Extracts
4.1 References to Other NEC Rules
4.2 References to Other Standards
4.3 Extracts
22
22
22
23
Chapter 5 Editorial Administrative Responsibilities
5.1 General
5.2 Responsibilities of Committee Members
5.3 Responsibilities of NFPA Staff
24
24
24
24
Annex A — Editorial Guidance on Exceptions
25
Annex B — Standard Terms
27
Annex C — Conversion Reference Table
37
Index
40
3
13
15
18
NATIONAL ELECTRICAL CODE (NEC®)
STYLE MANUAL
CHAPTER 1 GENERAL
1.1 Purpose. The National Electrical Code (NEC) Style Manual is prepared under the
guidance of the NEC Technical Correlating Committee and is used to advise members of
the Code-Making Panels on the required editorial style and arrangement of the NEC. It is
intended to be used as a practical working tool to assist in making the NEC as clear,
usable, and unambiguous as possible.
1.2 Scope. This Manual provides editorial and administrative requirements for writing
the National Electrical Code® (NFPA 70) and the Standard for Electrical Safety in the
Workplace (NFPA 70E). Except as otherwise specified in this manual, the NEC® and the
Standard for Electrical Safety in the Workplace shall comply with the Manual of Style for
NFPA Technical Committee Documents.
1.2.1 Requirements Not Included. The NEC Style Manual does not include
many purely editorial and stylistic matters, including, but not limited to, the formatting of
tables, capitalization practices, use of hyphens, and units of measurement. For
information on these editorial guidelines, see the Manual of Style for NFPA Technical
Committee Documents..
1.2.2 Format. The NEC is formatted differently from other NFPA standards.
Examples of these differences include, but are not limited to, arrangement of the
document, its internal numbering system, and use of informational notes. The Secretary
of the NEC Technical Correlating Committee shall be responsible for recommending to
the NEC Technical Correlating Committee resolutions of any apparent conflicts or
discrepancies between the Manual of Style for NFPA Technical Committee Documents
and this manual.
1.3 Regulatory Adoption. Because the National Electrical Code is intended to be
suitable for adoption as a regulatory document, it is important that it contain clearly
stated mandatory requirements in the Code text. This should encourage uniform adoption
of the National Electrical Code without alterations.
1.4 Examples. The examples shown throughout this manual are intended to be
representative of the style and arrangement of the text. The actual text used in the
example may or may not match the current document text.
4
CHAPTER 2 DOCUMENT STRUCTURE AND NUMBERING
2.1 Subdivisions of the NEC. The National Electrical Code shall be organized as
follows.
2.1.1 Introduction. Article 90 contains the scope of the NEC and administrative
provisions.
2.1.2 Chapters. Chapters are major subdivisions of the NEC that cover broad
areas and are divided into articles. Chapters shall be organized as follows:
Chapter 1 General
Article 100 — Definitions
Article 110 — Requirements for Electrical Installations
Chapter 2 Wiring and Protection
Articles 200 – 299
Chapter 3 Wiring Methods and Materials
Articles 300 – 399
Chapter 4 Equipment for General Use
Articles 400 – 499
Chapter 5 Special Occupancies
Articles 500 – 599
Chapter 6 Special Equipment
Articles 600 – 699
Chapter 7 Special Conditions
Articles 700 – 799
Chapter 8 Communications Systems
Articles 800 – 899
Chapter 9 Tables
2.1.3 Articles. Articles are chapter subdivisions that cover a specific subject
such as grounding, overcurrent protection, lighting fixtures, and so on. Each article shall
have a title. Articles are divided into sections and sometimes into parts.
5
2.1.4 Parts. If an article is sufficiently large, or where necessary to logically
group requirements, it shall be permitted to be subdivided into parts that correspond to
logical groupings of information. Parts shall have titles and shall be designated by
Roman numerals. (See example.) Parts typically consist of a number of sections; see
2.4.2.1 for section numbering in articles that are subdivided into parts.
Example:
I Installation
II Construction Specifications
III Grounding
2.1.5 Subdividing Sections. Sections shall be permitted to be subdivided for
clarity, with each subdivision representing either a rule or a part of a rule. Up to three
levels of subdivisions shall be permitted, and any level shall be permitted to contain a list.
2.1.5.1 List Formats. Lists are a method of structuring the items necessary to
complete a rule. Lists in any subdivision level shall be numbered, and listed items shall
be single words, phrases, or sentences. Items in a list shall not contain titles.
2.1.5.2 Subdivision Titles. First and second level subdivisions shall have titles.
Third level subdivisions shall be permitted to have titles.
6
2.1.5.3 Subdivision Example. The following illustrates typical subdivision
numbering with lists (see also 2.4):
Example:
Chapter — Chapter 2 Wiring and Protection
Article —
Article 250 — Grounding
Part —
II Conductors
Section —
250.121 Identification and Size of Equipment Grounding Conductors.
Unless otherwise required in this Code, equipment grounding conductors shall be
permitted to be bare, covered, or insulated.
Level 1 —
(A) Identification of Conductors. An insulated or covered conductor larger
than No. 6 copper or aluminum shall be permitted to be identified, at the time of
installation, by one of the following means:
List item —
List item —
List item —
(1) Stripping the insulation or covering from the entire exposed length.
(2) Coloring the exposed insulation or covering green.
(3) Marking the exposed insulation or covering with green tape or green
adhesive labels.
Level 1 —
(B) Size of Conductors.
Level 2 —
(1) General. Copper, aluminum, or copper-clad aluminum equipment
grounding conductors of the wire type shall not be smaller than shown in
Table 250.122.
Level 2 —
(2) Adjustment for Voltage Drop. If conductors are adjusted to compensate
for voltage drop, equipment grounding conductors shall be adjusted according to
circular mil area.
Level 2 —
(3) Conductors in Parallel. If conductors are run in parallel, the equipment
grounding conductors shall be sized by either of the following methods.
Level 3 —
(a) Each parallel equipment grounding conductor shall be sized on the
basis of the ampere rating of the overcurrent protective device. If
ground-fault protection for equipment is installed, each parallel equipment
grounding conductor run in a raceway shall be to be sized in accordance with
Table 250.122.
Level 3 —
(b) Parallel equipment grounding conductors in multiconductor cables
shall be permitted to be sized in accordance with the Table 250.122
on the basis of the trip rating of the ground-fault protection if the
following conditions are met:
List item —
List item —
List item —
(1) Only qualified persons will service the installation.
(2) The trip rating is not greater than the ampacity of a single conductor.
(3) The ground-fault protection is listed for the purpose.
7
2.1.6 Annexes. Annexes (previously known as appendixes) shall contain
references, examples, calculations, tables, and similar nonmandatory material. Annexes
do not form part of the requirements of the National Electrical Code, and a statement to
that effect shall appear at the beginning of each annex. Annexes shall have titles and
shall be designated by capital letters.
Example:
Annex C
Conduit and Tubing Fill for Conductors and Fixture Wires
of the Same Size
This annex is not a part of the requirements of this
Code but is included for informational purposes only.
Annexes that are used to cross-reference material from one edition of the Code to
another edition of the Code shall remain as an annex for a minimum of two code cycles.
NFPA staff shall have the responsibility of updating any cross-reference annex.
2.2 Content of NEC Subdivisions.
2.2.1 Scopes. Each article shall have a scope, which shall be the first section of
the article. The approval of article scope statements is the responsibility of the Technical
Correlating Committee.
Example:
Article 422 — Appliances
422.1 Scope
Article 280 — Surge Arresters
280.1 Scope
2.2.2 Definitions. Definitions shall be in alphabetical order and shall not contain
the term that is being defined. Definitions shall not contain requirements or
recommendations.
8
2.2.2.1 Article 100. In general, Article 100 shall contain definitions of terms that
appear in two or more other articles of the NEC.
Examples:
Enclosure. The case or housing of apparatus, or the fence or walls surrounding an
installation to prevent personnel from accidentally contacting energized parts, or
to protect the equipment from physical damage.
Ground. A conducting connection, whether intentional or accidental, between an
electrical circuit or equipment and the earth, or to some conducting body that
serves in place of the earth.
2.2.2.2 Definitions in Other Articles. If an article contains one or more
definitions, the definition(s) shall be in the second section, shall be listed in alphabetical
order, and shall be styled as shown in the following examples.
Examples:
280.2 Definition.
Surge Arrester. A protective device for limiting surge voltages by discharging or
bypassing surge current, and it also prevents continued flow of follow current
while remaining capable of repeating these functions.
318.2 Definition.
Cable Tray System. A unit or assembly of units or sections and associated
fittings forming a rigid structural system used to securely fasten or support cables
and raceways.
2.3 Tables and Figures.
2.3.1 Mandatory. Tables and figures, including any accompanying notes,
represent mandatory requirements, unless specifically noted as in 2.3.2. Tables and
figures shall be referenced in the text and shall be designated by the number of the NEC
rule in which they are referenced. Each table shall have a title and each figure shall have
a caption. Titles and captions shall be as brief as possible, consistent with clarity.
9
Example:
500.5(D) Marking. Approved equipment shall be marked to show the class,
group, and operating temperature referenced to a 40oC ambient. Numbers marked
on the equipment nameplates shall be in accordance with Table 500.5(D).
Table 500.5(D) Identification Numbers.
2.3.2 Nonmandatory. When the NEC is adopted into law, graphics in the text of
the document become mandatory. If a Code-Making Panel wishes to use a table or figure
to illustrate only a typical situation, not a mandatory requirement, that table or figure
shall be identified as an informational note or be placed in an annex. Each table shall
have a title and each figure shall have a caption.
2.4 Numbering Practices. The following two practices are intended to improve NEC
usability by preventing the continual renumbering of articles and sections from one
edition to the next.
2.4.1 Parallel Numbering Within Similar Articles. To the extent possible,
Code-Making Panels are encouraged to use the same section numbers (and part numbers,
where applicable) for the same purposes within articles covering similar subjects.
Example: A typical family of articles might be organized as follows:
Article 399 — Future Products
I General
399.1 Scope
399.2 Definition
399.3 Other Articles
II Installation
399.10 Uses Permitted
399.11 Uses Not Permitted
399.13 Bends
III Construction Specifications
399.20 General
399.21 Sizes
399.22 Marking
2.4.2 Nonconsecutive Numbering. Articles and sections in the NEC are, in
general, numbered consecutively. However, gaps or unused numbers are sometimes left
for future articles and sections. Assigning numbers to new articles is the responsibility of
the NEC Technical Correlating Committee, advised by the NFPA Staff Editor. Assigning
numbers to new sections within articles is the responsibility of Code-Making Panels,
advised by the NFPA Staff Editor.
10
2.4.2.1 Parts. If an article is subdivided into parts, it is recommended that the
section numbering within each part start with the next decade as a minimum.
Example:
Article 498 — Future Equipment
I General
498.1 – 498.6
II Disconnecting Means
498.10 – 498.24
III Branch-Circuit Conductors
498.50 – 498.58
IV Provisions for Combination Loads
498.100 – 498.110
2.4.3 Numbering Informational Notes. If there are two or more consecutive
informational notes, each shall be numbered.
Example
210.12 Arc-Fault Circuit-Interrupter Protection.
(A) Dwelling Units. All 120-volt, single phase, 15 and 20 ampere branch circuits
supplying outlets installed in dwelling unit family rooms, dining rooms, living
rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets,
hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit
interrupter, combination-type, installed to provide protection of the branch circuit.
Informational Note No.1: For information on types of arc-fault circuit
interrupters, see UL 1699-1999, Standard for Arc-Fault Circuit Interrupters.
Informational Note No.2: See 11.6.3(5) of NFPA 72-2010, National Fire Alarm
and Signaling Code, for information related to secondary power supply
requirements for smoke alarms installed in dwelling units.
Informational Note No.3: See 760.41(B) and 760.121(B) for power-supply
requirements for fire alarm systems.
2.5 General References to Other Articles. If a listing is made of references to other
articles under the section title “Other Articles,” the listing shall be in table format and
shall comply with 2.3.
2.6 Exceptions.
11
2.6.1 Placement and Order. Exceptions shall immediately follow the main rule
to which they apply. Where exceptions are made to items within a numbered list, the
exception shall clearly indicate the items within the list to which it applies. Exceptions
containing the mandatory terms shall or shall not are to be listed first in the sequence.
Permissive exceptions containing shall be permitted are to follow any mandatory
exceptions and be listed in their order of importance as determined by the Code-Making
Panel.
2.6.2 Numbering. Where there are two or more consecutive exceptions, each
shall be numbered.
12
CHAPTER 3 EDITORIAL GUIDELINES
3.1 Mandatory Rules, Permissive Rules, and Explanatory Information.
3.1.1 Mandatory Rules. Shall, shall not, and shall not be indicate mandatory
NEC rules. Terms such as is to be, shall be not, and must, whose meanings are less clear,
shall not be used. The terms may or can shall not be used.
3.1.2 Permissive Rules. Shall be permitted and it shall be permissible indicate
allowed optional or alternate methods. (Note that these are still mandatory language and
constitute rules.) The term may shall only be used where it recognizes a discretionary
judgment on the part of an authority having jurisdiction.
Example:
The authority having jurisdiction may waive specific requirements
in the Code or permit alternate methods.
3.1.3 Informational Notes. Informational notes contain explanatory information
and shall be located directly after the rule they apply to. Informational Notes shall not be
written in mandatory language and shall not contain requirements, make interpretations,
or make recommendations. If an Informational Note is needed to explain the text of the
code, consideration should be given to rewriting the text of the code to make the rule
clear.
Examples of informational notes
Correct (D) 600 Volts Between Conductors. Circuits exceeding 277 volts, nominal, to
ground and not exceeding 600 volts, nominal, between conductors shall be permitted to
supply the following:
(1) The auxiliary equipment of electric-discharge lamps mounted in permanently
installed luminaires where the luminaires are mounted in accordance with one of the
following:
a. Not less than a height of 6.7m (22ft) on poles or similar structures for the
illumination of outdoor areas such as highways, roads, bridges, athletic fields or parking
lots
b. Not less than a height of 5.5m (18ft) on other structures such as tunnels
Informational Note: See 410.138 for auxiliary equipment limitations
(2) Cord-and-plug-connected or permanently connected utilization equipment other than
luminaires
13
(3) Luminaires powered from direct-current systems where the luminaire contains a
listed, dc-rated ballast that provides isolation between the dc power source and the lamp
circuit and protection from electric shock when changing lamps.
Incorrect (D) 600 Volts Between Conductors. Circuits exceeding 277 volts, nominal,
to ground and not exceeding 600 volts, nominal, between conductors shall be permitted
to supply the following:
(1) The auxiliary equipment of electric-discharge lamps mounted in permanently
installed luminaires where the luminaires are mounted in accordance with one of the
following:
a. Not less than a height of 6.7m (22ft) on poles or similar structures for the
illumination of outdoor areas such as highways, roads, bridges, athletic fields or parking
lots
b. Not less than a height of 5.5m (18ft) on other structures such as tunnels
(2)
Cord-and-plug-connected or permanently connected utilization equipment other
than luminaires
(3)
Luminaires powered from direct-current systems where the luminaire contains a
listed, dc-rated ballast that provides isolation between the dc power source and the lamp
circuit and protection from electric shock when changing lamps.
Informational Note: See 410.138 for auxiliary equipment limitations.
3.1.4 Exceptions. Exceptions to NEC rules shall be used sparingly. If used,
exceptions shall convey alternatives or differences to a basic code rule. It is the
responsibility of the Code-Making Panel to determine whether the principle can be
expressed most effectively as a separate positive code rule or as an exception to a rule.
Annex A contains commentary on exceptions.
3.1.4.1 Language. Exceptions shall be permitted to use the terms shall, shall
not, or shall be permitted depending on whether they specify a mandatory requirement
that is (1) different from the rule, or (2) diametrically opposite to the rule, or (3) whether
they permit, but do not require, a variance from the main rule. Exceptions shall be
written in complete sentences.
3.1.4.2 Excessive Numbers of Exceptions. When the number of exceptions to a
specific code rule becomes excessive, the Code-Making Panel should consider a revision
of the basic rule or a rearrangement of the section to better convey the objectives.
14
3.2 Word Choices.
3.2.1 Unenforceable Terms. The NEC shall not contain references or
requirements that are unenforceable or vague. The terms contained in Table 3.2.1 shall
be reviewed in context, and, if the resulting requirement is unenforceable or vague, the
term shall not be used.
Table 3.2.1 Possibly Unenforceable and Vague Terms
Many
May
Maybe
Might
Most(ly)
Near(ly)
Neat(ly)
Normal(ly)
Note
Periodic(ally)
Practical(ly)
Practices
Prefer(red)
Proper(ly)
Ready(ily)
Reasonable(y)
Safe(ly)(ty)
Satisfactory
Secure(ly)
Several
Significant
Similar
Substantial(ly)
Sufficient(ly)
Suitable
Usual(ly)
Workmanlike
Acceptable
Adequate
Adjacent
Appreciable
Appropriate
Approximate(ly)
Available
Avoid(ed)
Can
Care
Careful(ly)
Consider(ed)(ation)
Could
Designed for the purpose
Desirable
Easy(ily)
Equivalent(ly)
Familiar
Feasible
Few
Frequent(ly)
Firmly
Generally
Good
Lightly
Likely
Legible(y)
Examples of unenforceable or vague terms:
Correct: A manual pull station shall be located within 1 m of each exit.
Incorrect: A manual pull station shall be located near each exit.
Correct: Conduit shall be supported at intervals not exceeding 10 ft.
Incorrect: Conduit shall be adequately supported at periodic intervals.
15
3.2.2 Expressing Maximum and Minimum Limits. Maximum and minimum
limits shall be expressed with the following types of wording.
Examples:
Shall not exceed 300 volts to ground . . .
Shall have a clearance of not less than 5 cm . . .
Shall be supported at intervals not exceeding 1.5 m . . .
3.2.3 Acronyms and Uncommon Abbreviations. All acronyms and any
abbreviations that are not in common use shall be spelled out with the abbreviation
following in parentheses for the first use of the term in the body of each article. Each
subsequent use in the article shall be permitted to be the acronym or abbreviation only.
Examples:
(A) Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles
installed in the locations specified below shall have ground-fault circuit-interrupter
(GFCI) protection for personnel.
(B) Nondwelling Units. All 125-volt, single-phase, 15- and 20-ampere
receptacles installed in the locations specified below shall have GFCI protection for
personnel.
3.2.4 Standard Terms. Standard terms have been established through accepted
use or by definition and are to be used in preference to similar terms that do not have
such recognition. Annex B provides guidance for syntax, spelling, punctuation, and usage
of many standard technical terms.
3.2.5 Special Terms.
3.2.5.1 Ampacity. The term ampacity, as defined in Article 100, applies to the
current-carrying capacity of conductors only. Therefore, this term shall be used in this
sense, but only in this sense. (The ampacity of a No. 14 copper conductor with 60°C
insulation is 20.) On the other hand, switches, motors, and similar equipment are not
rated in ampacities. Instead, they have current ratings, voltage ratings, horsepower
ratings, and so on. Such equipment, therefore, shall not be specified or referred to in
“ampacity” values.
3.2.5.2 Authority Having Jurisdiction. The term used to indicate any kind of
inspection authority, enforcement authority, or the like, shall be the authority having
jurisdiction. The use of this term will result in standardization, and it is in keeping with
the term used in all other NFPA standards. This term is fully developed and explained in
Paragraph 3-3.6.1 of the “NFPA Regulations Governing Committee Projects.”
16
3.2.5.3 Listed by a Nationally Recognized Testing Laboratory. Use of the
terms "Nationally Recognized Testing Laboratory" or "NRTL" shall be avoided. The
definition of "listed" in Article 100 provides the details necessary for application in the
NEC. The Nationally Recognized Testing Laboratory program, also known as NRTL, is
an OSHA program for the accreditation of laboratories that test products for the
workplace and is not to be applied generally in the NEC. When used in NFPA 70 the
term “Qualified Electrical Testing Laboratory” is preferred.
3.2.5.4 Provisions on Guarding. Requirements for guarding shall be stated in as
complete a manner as possible and in as nearly standardized form as can be reasonably
achieved. For example, the two terms protected against contact with live parts and
protected against accidental contact with live parts do not mean the same thing. It may
be necessary for qualified persons to have access to live parts, or it may be desirable to
provide varying degrees of protection, depending on the location. Among other things,
this distinction could affect the type of ventilation louvers or drains that would be
acceptable for some types of equipment. The intent of the type and degree of protection
to be required should, therefore, be made clear if possible.
3.2.5.5 Provisions on Protection Against Physical Damage. If protection
against physical damage is to be one of the requirements, this can be standardized by the
use of this terminology instead of using the phrase provided with mechanical protection
to mean the same thing. In many cases, one or two acceptable methods of providing the
intended protection can be stated as examples for better understanding without restricting
the rule to a specification-type requirement. There have been some cases, such as in the
instance of grounding electrode conductors, where the means provided by the installer for
protection against physical damage has impaired the electrical function of the conductor
or equipment. This can be largely avoided by an explanatory note if the intent cannot be
otherwise made sufficiently clear.
3.2.5.6 Voltage. The term voltage is well understood and shall be used in
preference to other terms such as potential. Because voltage is expressed in volts, a
requirement should be written to avoid repetition of this term if it is possible to do so
without losing clarity.
Example:
Correct: A circuit supplying the primary of an isolating transformer shall not
exceed 300 volts between conductors.
Incorrect: The voltage of a circuit supplying the primary of an isolating
transformer shall not exceed 300 volts between conductors.
3.2.6 Formulas and Equations. Formulas and equations shall be expressed in
standard mathematical symbols.
17
3.2.7 Units of Measurement.
3.2.7.1 Measurement System of Preference. Metric units of measurement are
in accordance with the modernized metric system known as the International System of
Units (SI).
3.2.7.2 Dual System of Units. The SI units shall appear first, and the inch-pound
units shall immediately follow in parenthesis. In tables the SI and inch-pound units shall
appear in separate columns.
3.2.7.3 Permitted Uses of Soft Conversion.
3.2.7.3.1 Trade Sizes. Where the actual measured size of a product is not the
same as the nominal size, trade size designators shall be used rather than dimensions.
Trade practices shall be followed in all cases.
3.2.7.3.2 Extracted Material. Where material is extracted from another
standard, the context of the original material shall not be compromised or violated. Any
editing of the extracted text shall be confined to making the style consistent with that of
the NEC.
3.2.7.3.3 Industry Practice. Where industry practice is to express units in inchpound units, the inclusion of SI units shall not be required.
3.2.7.3.4 Safety. Where hard conversion to SI would have a negative impact on
safety.
3.2.7.4 Approximate Conversion. The conversion from inch-pound units to SI
units shall be permitted to be an approximate conversion.
3.2.7.5 Standard Conversions. See Annex C for information on standard
conversions.
3.2.7.6 Units. For dimensions less than 1 m, the SI unit shall be expressed as
mm. For dimensions from 1 m to less than 1 km, the SI units shall be expressed in m. For
dimensions of 1 km or greater, the SI units shall be expressed as km.
3.3 Writing Style. These guidelines shall be
followed to help produce clear, unambiguous, NEC language.
3.3.1 General Guidelines.
18
1. Write in present tense; do not write in future tense.
Example:
Correct: No conductor shall be used in such a manner that its operating temperature
exceeds that designated for the type of insulated conductor involved.
Incorrect: No conductor shall be used in such a manner that its operating temperature
will exceed that designated for the type of insulated conductor involved.
2. Use simple declarative sentence structure, and keep sentences short. Writing
rules in long sentences full of commas, dependent clauses, and parenthetical expressions
often creates confusion and misunderstanding. The requirement can be written in two or
more short sentences, expressed using a list or table, or both.
Example:
Correct:
(D) Grounded and Grounding Conductors. If a circuit supplies portables or pendants
and the circuit includes a grounded conductor, then the following shall apply.
1. Receptacles, attachment plugs, connectors, and similar devices shall be of
the grounding type.
1. The grounded conductor of the flexible cord shall be connected to the
screw shell of any lampholder or to the grounded terminal of any
utilization equipment supplied.
Incorrect:
(D) Grounded and Grounding Conductors. Where a circuit supplies portables or
pendants and includes a grounded conductor as provided in Article 200, receptacles,
attachment plugs, connectors, and similar devices shall be of the grounding type, and the
grounded conductor of the flexible cord shall be connected to the screw shell of any
lampholder or to the grounded terminal of any utilization equipment supplied.
3. Use common words and avoid overly complex terminology (see
3.3.4).
4. Use positive language, rather than negative, wherever possible.
Example:
Correct: Boxes used in wet locations shall be listed for wet locations.
Incorrect: Ordinary electrical boxes shall not be used in wet locations.
19
5. If possible, avoid using dependent clauses, parenthetical phrases, and unclear
inverted word order.
Example:
Correct: The definitions in Part I of this article apply throughout the
Code.
Incorrect: Part I of this article contains definitions intended to apply
wherever the terms are used throughout this Code.
3.3.2 Lists and Tables. If possible, use lists or tables to present requirements,
rather than long text descriptions.
3.3.3 Plural. Unless referring to a single item of equipment, references to
electrical components and parts shall be plural rather than singular. This results in
greater consistency and makes it clear that the NEC provision refers to all components or
parts of a given type or class.
Examples:
Correct
Luminaires
Receptacles
Switches and circuit breakers
Outlet boxes and enclosures
Installations shall...
Incorrect
a luminaire
a receptacle
a switch or circuit breaker
an outlet box or enclosure
an installation shall...
3.3.4 Word Clarity. Words and terms used in the NEC shall be specific and
clear in meaning, and shall avoid jargon, trade terminology, industry-specific terms, or
colloquial language that is difficult to understand. NEC language shall be brief, clear,
and emphatic. The following are examples of old-fashioned expressions and word uses
that shall not be permitted:
Above or below (referring to text) — avoid using to describe the location of text.
Example:
Correct: ...shall be in accordance with (a), (b), and (c).
Incorrect: ...shall be in accordance with (a), (b), and (c) below.
20
And such, and the like — it is preferable to rearrange the sentence to use such as
followed by examples.
As allowed — Use allowed instead.
Herein — Usually this word can be dropped without affecting clarity.
Otherwise say “in this section” or whatever else is actually meant by herein.
If - Use to indicate a condition
Provided that — Use if instead.
Thereof — Rewrite sentence to say of or of them.
Utilize — Use use instead.
When - Use to express time.
Where — Use to convey a location or a situation. Not to be used to express time.
3.3.5 Parallel Construction. Parallel construction means stating similar
requirements in similar ways for greater consistency. This helps makes the NEC clear for
users. Lack of consistency often creates confusion, causing users to ask: Does this
difference in wording represent a different requirement? Or is it simply two different
ways of trying to say the same thing? There are several kinds of parallel construction:
Organization and Numbering. If practicable, the subsections of similar articles
should be numbered in the same order (see 2.4.1).
Sections. Different sections, within the same article, that reflect similar or closely
related subjects, should have similar structures.
Lists. All items in a list should be parallel (that is, singular or plural, written in
the same verb tense, using phrases or sentences but not a mix).
21
CHAPTER 4 REFERENCES AND EXTRACTS
4.1 References to Other NEC Rules. Use references to improve clarity of the rule.
Avoid redundant use of references. Do not use a reference if the requirement is already
covered by 90.3. Explanatory references shall be in informational notes.
4.1.1 References to a Part Within an Article. References shall not be made to
an entire article, such as “grounded in accordance with Article 250” unless additional
conditions are specified. References to parts within articles shall be permitted.
Example:
If a switch or circuit breaker serves as the disconnecting means, it shall be within sight
from the motor controller and shall comply with Part IX of Article 430.
4.1.2 Other References. Use references to other NEC rules to avoid repeating a
requirement. If used, references shall include only the number of the rule being
referenced; the words section, subsection, and paragraph shall not be used. References
shall indicate the subject of the rules being referenced; the subject shall follow the
number.
Example:
Wiring and equipment in Class I, Division 1 locations shall be grounded as specified in
Article 250 and with the following additional requirements...
Informational Note: See 336.10 for the definition of first floor.
Informational Note: See 440.22(B)(2), Exception No. 2, for branch-circuit
requirements for cord- and plug-connected equipment.
4.2 References to Other Standards. References to other standards shall not be in
mandatory Code text. References to product standards shall be in an informative annex.
References to other Standards shall be in the Informational Notes.
22
4.3 Extracts.
4.3.1 Extracting Material from an NFPA Document and Including It in the
NEC. Extracting provides an advantage over multiple references to requirements
contained within other NFPA documents. Extracting has the disadvantage of creating a
situation where the text of the source document and the user document are not identical
due to different revision cycles.
4.3.2 Extract Requirements. To extract material from another NFPA
document, the following requirements shall be met.
4.3.2.1 Reason. There shall be a specific technical reason for the extract.
4.3.2.2 Context. A section or paragraph being extracted from another document
shall represent a complete thought and shall be entirely extracted. The context of the
original material shall not be compromised or violated. Any editing of the extracted text
shall be confined to making the style consistent with that of the NEC and then only with
the concurrence of the committee having primary jurisdiction. Such concurrence shall be
obtained through the staff liaison for the source document.
4.3.2.3 Identification. The number, title, and edition of the NFPA document
from which the extract is taken shall appear at the beginning of the article in which the
extract is used. The document number and paragraph from which the extract is taken
shall appear in brackets at the end of the section in which the extract is used.
Example:
Article 514 — Gasoline Dispensing and Service Stations
Informational Note: Rules that are followed by a reference to [NFPA 30, xxx]
in brackets contain text that has been extracted from NFPA 30-1996, Automotive
and Marine Service Station Code (xxx represents the specific sections of that
document referenced). Only editorial changes were made to the extracted text to
make it consistent with this Code.
514.2 Class I Locations. Table 514.2 shall be applied where Class I liquids are
stored, handled, or dispensed and shall be used to delineate and classify service
stations. A Class I location shall not extend beyond an unpierced wall, roof, or
other solid partition.
[NFPA 30, 7-1 and 7-3].
514.5(B) Attended Service Stations. Emergency controls as specified in
Section 514.5(A) shall be installed at a location acceptable to the authority having
jurisdiction (AHJ), but controls shall not be more than 100 ft (30 m) from
dispensers. [NFPA 30, 9-4.5]
4.3.3 Interpretations of Extracted Material in the NEC. Requests for
interpretations of, or proposed revisions to, the extracted text shall be referred to the
NFPA technical committee that is responsible for the source document.
23
CHAPTER 5 EDITORIAL ADMINISTRATIVE RESPONSIBILITIES
5.1 General. Both NFPA committee members and staff shall be responsible for ensuring
compliance with this manual.
5.2 Responsibilities of Committee Members.
5.2.1 Code-Making Panels. Panels shall be responsible for ensuring that the
Code text agreed on at meetings complies with all requirements of this manual. They
shall rely on the guidance of NFPA staff.
5.2.2 NEC Technical Correlating Committee. The NEC Technical Correlating
Committee shall act as needed to ensure that all text appearing in the Report on Proposals
(ROP), Report on Comments (ROC), and final National Electrical Code meets the
requirements of this Manual.
5.3 Responsibilities of NFPA Staff.
5.3.1 NEC Staff Editor. NFPA shall assign a staff editor to assist the NEC
Technical Correlating Committee in developing the final text of the NEC. This editor
shall be responsible for advising committees, panel liaisons, and the NEC Technical
Correlating Committee Secretary on matters of NEC style.
5.3.2 Panel Liaisons. NFPA staff serving at meetings of Code-Making Panels
shall advise panels on matters of NEC style.
5.3.3 NEC Technical Correlating Committee Secretary. The Secretary shall
be responsible for advising the NEC Technical Correlating Committee on creating Code
text that complies with the requirements of this manual. If text approved by CodeMaking Panels does not comply, the Secretary shall recommend administrative revisions
needed to bring the text into compliance, while preserving the panel’s intent.
24
Annex A
Editorial Guidance on Exceptions
Exceptions should be re-written into positive language, if positive language achieves
clarity. The elimination of all exceptions is not intended, nor is it desirable. In some
cases, deleting the word exception and incorporating the unedited language into a main
rule may not lead to clarity. The resulting rule may appear to be self-contradicting
instead.
But, in many cases, positive language is much clearer. Two good examples may be
found in Sections 240-3 and 240-21. In these instances, the Code language once
consisted of a short main rule followed by a number of exceptions.
Other good examples of writing exceptions into positive language may be found in the
ROP for the 1999 Code cycle. Proposed 520-68(A) consisted of a main rule with four
exceptions. The main rule was changed to (1) entitled “General.” It is clear that this rule
would generally apply. The exceptions then became (2) stand lamps, (3) high
temperature applications, and (4) breakouts. In 520-68(B), an exception was clearly the
easiest way to deal with the difference from the main rule, and Panel 15 retained the
exception.
520.68. Conductors for Portables.
(A) Conductor Type.
(1) General. Flexible conductors, including cable extensions, used to supply
portable stage equipment shall be listed extra-hard usage cords or cables.
(2) Stand Lamps. Reinforced cord shall be permitted to supply stand lamps
where the cord is not subject to severe physical damage and is protected by an
overcurrent device rated at not over 20 amperes.
Exceptions No. 1. Reinforced cord shall be permitted to supply stand lamps
where the cord is not subject to severe physical damage and is protected by an
overcurrent device at not over 20 amperes.
(3) High Temperature Applications. A special assembly of conductors in
sleeving no longer than 3.3 ft (1 m) shall be permitted to be employed in lieu of flexible
cord if the individual wires are stranded and rated not less than 125oC (257oF) and the
outer sleeve is glass fiber with a wall thickness of at least 0.025 in. (0.635 mm).
Portable stage equipment requiring flexible supply conductors with a higher
temperature rating where one end is permanently attached to the equipment shall be
permitted to employ alternate, suitable conductors as determined by a qualified testing
laboratory and recognized test standards.
Exception No. 2: A special assembly of conductors in sleeving no longer than 3.3
ft. (1 m) shall be permitted to be employed in lieu of flexible cord if the individual wires
are stranded and rated not less than 125 degrees C (257oF) and the outer sleeve is glass
fiber with a wall thickness of at least 0.025 in. (0.635 mm).
Exception 3: Portable stage equipment requiring flexible supply conductors with a
higher temperature rating where one end is permanently attached to the equipment shall
be permitted to employ alternate, suitable conductors as determined by a qualified testing
laboratory and recognized test standards.
(4) Breakouts. Listed, hard usage (junior hard service) cords shall be permitted
in breakout assemblies where all of the following conditions are met:
a. The cords are utilized to connect between a single multiple connector
containing two or more branch circuits and multiple two-pole, 3-wire connectors.
b. The longest cord in the breakout assembly does not exceed 20 ft (6.1 m).
25
c. The breakout assembly is protected from physical damage by attachment over
its entire length to a pipe, truss, tower, scaffold, or other substantial support structure.
d. All branch circuits feeding the breakout assembly are protected by overcurrent
devices rated at not over 20 amperes.
Exception No. 4: Listed, hard usage (junior hard service) cords shall be permitted
in breakout assemblies where all of the following conditions are met:
a. The cords are utilized to connect between a single multipole connector
containing two or more branch circuits and multiple two-pole, 3-wire connectors.
b. The longest cord in the breakout assembly does not exceed 20 ft. (6.1 m).
c. The breakout assembly is protected from physical damage by attachment over
its entire length to a pipe, truss, tower, scaffold, or other substantial support structure.
d. All branch circuits feeding the breakout assembly are protected by overcurrent
devices rated at not over 20 amperes.k
b. Conductor Ampacity. The ampacity of conductors shall be as given in
Section 400-5, except multiconductor listed extra-hard usage portable cords, that are not
in direct contact with equipment containing heat-producing elements, shall be permitted
to have their ampacity determined by Table 520-44. Maximum load current in any
conductor shall not exceed the values in Table 520-44.
Exception: Where alternate conductors are allowed in Section 520-68(a)(3),
Exception Nos. 2 and 3, their ampacity shall be as given in the appropriate table in this
Code for the types of conductors employed.
26
Annex B
Standard Terms
The following list provides guidance for syntax, spelling, punctuation, and usage for
many of the standard terms used in the NEC. Many words are listed with an abbreviation
to indicate usage. For example, adjective = a, noun = n, and verb = v.
A
abovegrade (a)
aboveground (a)
acknowledgment (no e)
adapter
adjustable-speed (a)
affect (v) = to influence; effect (n) = result
air conditioner (n)
air-condition (v)
air-conditioning (a)
airflow (a,n)
airtight (a)
airspace (a)
air-handling (a)
alternating current (n) (abbrev. ac)
alternating-current (a) (abbrev. ac)
American Wire Gage (abbrev. AWG)
ampacity
ampere (see units of measurement)
20-ampere–rated receptacle
and/or (try to avoid)
apparatus (singular and plural)
approved
arc fault (n)
arc-fault(a)
arrester (not arrestor)
at least (avoid; use not less than to indicate minimum dimension)
autoignition
authority having jurisdiction (abbrev. AHJ)
automatic-reset (a)
B
backfeed
backfill (n,v)
backup (a,n)
back-wiring spaces
belowgrade (a)
belowground (a)
bipolar
braid-covered (a)
branch circuit (n)
branch-circuit (a)
branch-circuit ground-circuit
branch-circuit overcurrent device
buildup (n)
build up (v)
busbar
buses
busing
C
cable tray
cablebus
capacitors
27
ceiling-suspended (paddle) fan
circuit-grounding connection
circuit-interrupting device
circuit-protective device
circular mil (a)
Class I location
Class I, Division 2, location
clean-up (n)
cleanup (v)
closed-circuit (a)
Code (initial cap and italic when referring to the NEC)
cold-storage warehouse
combination-load equipment
common-return (a)
communications system, utilities, equipment, and so on (not communication)
concrete-encased electrode
conductive-film heating elements
continuous current rating
control boards
control circuit (a)
constant-current systems
copper (Cu)
copper-clad (a)
cord- and plug-connected appliances
corner-grounded delta systems
corrosion-resistant (a)
counter space
counter-mounted (a)
countertop
crawl space
cross members
cross-connect arrays
cross section (n)
cross-sectional (a)
cubic inches (in.) (see units of measurement)
current-carrying (a)
current-limiting (a)
cut off (v)
cutoff (a,n)
cutouts (n)
D
data (singular and plural, use with plural verb)
dead-front switchboards
de-energize
deicing
delta [use symbol (∆) in equations]
delta-connected (a)
delta corner grounded
derating
Design B motor
dipole (a)
direct buried (n)
direct-buried (a)
direct current (n) (abbrev. dc)
direct-current (a) (abbrev. dc)
disconnecting means (not disconnection means)
dripproof
drywall
dual-element fuses
ducts (as in air-handling ducts, not for use with raceways)
ductwork
28
dust-ignitionproof (a)
dustproof (a)
dusttight (a)
E
effect (n) = result; affect (v) = to influence
e.g. (avoid using, use instead for example)
electric/electrical (use to be determined by staff)
electrical (as applied to requirements, standards, codes)
electric-discharge lighting
energized (electrically connected to a source of voltage
engine–generator set
ensure (not insure)
equipment (singular and plural)
equipment grounding conductor
etc. (try to avoid, use and so on, and so forth, or such as)
Exception No. 1 (when referring to specific exception)
Exception Nos. 1 and 2 (more than one exception)
exception (general, lowercase if used alone)
explosionproof
extra-hard usage
F
faceplate (n)
face-up position
fault-interrupting device
fault–current forces
fiberglass reinforced
field connection box
field-installed (a)
fire alarm circuit
fire-extinguishing equipment
fire-resistant construction
fireproof
firestopped
fixed, electric space-heating equipment
fixed-load (a)
fixed stage equipment
flame retardant (n)
flame-retardant (a)
flat-top raceways
fluxes
foamed-in-place material
forced-air system
full-load current
full-load rating
full-voltage resistor
fuseholder
G
gal (plural), 3-gal (a)
gas–air (a)
gauge, not gage
general-purpose (a)
general-use (a)
gray buses
grain-drying systems
grid-connected systems
grille
ground-fault circuit interrupter (n) (abbrev. GFCI)
ground-fault circuit-interrupter (a) (abbrev. GFCI)
ground-fault (a)
29
ground fault (n)
ground-fault protective device
grounding electrode conductor
guarding
guest rooms
H
hand-carried (n)
hand-held (a)
hand-supported (a)
handhole (n)
handlamp (n)
hazardous (classified) location
headroom (n)
heat-generating equipment
heat-resistant (a)
heavy-duty (a)
hertz (rather than cycles per second) (see units of measurement)
high-heat type
high-impedance grounded neutral system
high-leg (a)
high-pressure (a)
high-tension (a)
higher-rated (a)
horsepower (see units of measurement)
hour (do not abbreviate)
I
i.e. (avoid using, use that is)
if (indicates condition -- can usually be used instead of provided, provided that, or where)
igniter
ignitible (not ignitable)
impedance
impedance grounded neutral system
in-between (a,n)
indexes (not indices)
informational note (lower case when used alone in text)
inrush current
instantaneous-trip (a)
internal-combustion-driven (a)
K
knob-and-tube wiring
L
lampholder
lead-sheathed (a)
less-flammable transformers
let-through (n)
light-emitting diode (abbrev. LED)
likely (use instead of liable)
likely to become energized -- failure of insulation on
line-to-ground fault current
line-to-neutral loads
liquidtight (a)
live parts (electric conductors, buses, terminals, or components that are uninsulated or
exposed and shock hazard exists)
load-interrupter (a)
load-side (a)
locked-rotor (a,n)
locknut (n)
long-time rating
30
low-power-factor (a)
low-voltage (a)
lower-rated (a)
M
make-or-break (a)
manhole
maximum
meatpacking (a,n)
messenger-supported (a)
metal (instead of metallic)
metal-clad (a)
metal-enclosed switchgear (n)
metal-sheathed (a)
metal-shield connectors (n)
metallic (use only when directly related to material)
mineral-insulated (a)
minimum
minute (do not abbreviate)
mixer–amplifier (n)
motor control (a)
motor-circuit switch (n)
motor-compressors (n)
motor-driven (a)
motor-generator (a)
motor-generator set (abbrev. MG set)
motor-starting currents
multibuilding
multiconductor (instead of multiple-conductor or multi-conductor)
multimedia
multioutlet
multiphase
multipole
31
N
nameplate
nameplate rating load
NEC ® (always italic, with registered trademark on first reference)
network-powered (a)
No. 20 gauge sheet metal
non–current-carrying (a)
non–grounding-type (a)
non–power-limited (a)
nonaccessible
noncontinuous
noncurrent
nondwelling unit (a)
nonexplosionproof
nonflexible
noninductive
noninterchangeability
nonmetallic
nonmetallic-sheathed (a)
nonshielded cable
nontime
not over (instead of not more than)
not exceeding (instead of not more than)
not less than
O
off-premises source
oil-break (a)
oil-filled reactors
on-premises source
open-conductor supports
open-resistance (a)
optical fiber (a)
other than a dwelling unit (avoid, use nondwelling)
overcurrent device
overcurrent protective device
overtemperature (n)
over-temperature (a)
overvoltage (n)
P
panelboard
parallel (instead of multiple conductors)
part-winding start induction
pendant
phase-to-phase (a)
photovoltaic
plug-in units
pole-mounted (a)
positive-pressure ventilation
power conversion system (abbrev. PCS)
power factor (abbrev. PF)
power-conditioning unit (abbrev. PCU)
power-limited (a)
power-supply cord
practicable (means feasible)
practical (means useful)
pre-amplifier
pressure terminal connectors
pressure splicing connectors
protection against physical damage (state conditions)
protector
32
PVC-coated (a)
R
raceway
re-fused (a)
rectifier-derived dc system
remote-control (a)
resistance temperature device (abbrev. RTD)
resistor
revolutions per minute (abbrev. rpm)
road show (a,n)
root-mean-square (a)
runoff (n)
S
screw shell
screw shell devices
second (referring to time; do not abbreviate)
secondary-circuit fault protection
secondary-to-primary (a)
semiconducting (a)
service-disconnect enclosure
service disconnecting means
service-drop conductors
service-entrance conductors
service-lateral conductors
service-supplied ac (a)
set screw type (a)
set screw (n)
sheet metal (a)
short circuit (n)
short-circuit and ground-fault protective device
short-circuit current ratings
short-time duty
shunt-trip
sidelight
side-wiring spaces
silicon controlled rectifier (abbrev. SCR)
single-conductor cable
single-phase (not 1-phase, but 2-phase, 3-phase, etc.)
single-pole (a)
skin-effect heating
small-appliance branch circuit
solid-state (a)
space-heating equipment
specific-purpose (a)
stage-lighting (a)
stage set lighting
steady-state current
steel-frame (a)
storage battery charging equipment
strain-relief (a)
strut-type (a)
sunlight-resistant (a)
sunroom
supply-side equipment
surface metal raceway
surge arrester (n)
surge-arrester (a)
surge-protective capacitors
switchboards
33
T
tamper-resistant (a)
temperature-rated (a)
tenpenny nail
that (use where phrase is directly related to statement; do not set off with comma)
through (instead of thru or from and to)
time-current characteristics
time-delay fuse
toward (not towards)
trip-type (a)
turnbuckle (n)
Type MI cable
U
under-carpet (a)
upon (overused, try to avoid; on usually correct)
V
voltage
voltage-drop (a)
volt (see units of measurement)
voltmeter
W
wall switch-controlled (a)
weatherproof
wet-pit (n)
when (condition of time)
where (location or situation)
which (additional information in a phrase; set off with commas)
3-wire (a)
wire-bending space
workmanlike (avoid, unenforceable)
workplace
workspace
wye circuit (n)
wye-connected (a)
X
X-ray (not X-Ray)
34
Units of Measurement
Code text
In the Code text, all units of measure, when accompanied by a number value, will be styled as follows:
feet (foot)
meter
inch
centimeter
millimeter
square feet
square meter
square inch
square centimeter
cm2
square millimeter
mm2
cubic feet per minute
pounds
kilograms
degrees Celsius
degrees Fahrenheit
degree (angle)
percent
thousand circular mils
horsepower
hertz
kilovolt
kilowatt
kilovolt-amperes
kilovolt-amperes reactive
volt
ampere
watt
volt-ampere
megavoltampere
milliampere
millivolt
millivoltampere
milliwatt
micrometer
microjoule
joule
kilojoule
kJ
gallon
ft
m
in.
cm
mm
ft2
m2
in.2
ft3/min
lb
kg
℃
℉
degrees
percent
kcmil
hp (spelled out in heads)
Hz
kV
kW
kVA
kVAr
volt [abbreviate volt (V) when used with a number to mean rating]
ampere
watt
volt-ampere (spell out in heads)
MVA
mA
mV
mVA
mW
µm
µJ
J
gal
Display text (tables, figure callouts, equations, and examples)
Units of measure are abbreviated as follows in display text. Exception: If units are used without a number
preceding in a table title or table column head, units should be spelled out.
kilovolt
kilowatt
volt
ampere
volt-ampere
kilovolt-ampere
percent
thousand circular mils
degrees Celsius
degrees Fahrenheit
Hyphenation
kV
kW
V
A
VA
kVA
%
kcmil
℃
℉
35
Hyphenate all units of measurement when used as adjectives before a noun, except when multiple units of
measurement are used in the same phrase.
Example:
a 5.5-kW, 240-V dryer
a 2 in. x 2 in. x 2 in. box
Numbers
0.1 (use place-holding number before decimal)
0 through 2000 (use through to express range)
1000 (no comma in 4-digit numbers)
10,000
2 ½ (use case fraction)
first (not 1st)
Words or Terms Defined
When words or terms are used as themselves, they are italic.
Examples:
See Article 100 for a definition of bonding jumper.
The term minimum is used in the requirement.
36
Annex C
Conversion Reference Table
U.S. Customary
Unit
1
/32 in.
0.06 in.
0.0625 in.
1
/16 in.
0.090 in.
1
/8 in.
¼ in.
0.375 in.
3
/8 in.
½ in.
5
/8 in.
¾ in.
15
/16 in.
1 in.
1 ¼ in.
1 ½ in.
1 ¾ in.
1 7/8 in.
2 in.
2 1/8 in.
2 ¼ in.
2 3/8 in.
2 ½ in.
3 in.
3 ½ in.
3 ¾ in.
4 in.
4 ½ in.
4 11/16 in.
5 in.
5 ½ in.
6 in.
6 ½ in
7 in
7 ½ in.
8 in.
8 ½ in.
9 in.
10 in.
11 ½ in.
12 in.
13 in.
14 in.
Existing SI Unit
Proposed SI Unit
0.8 mm
1.5 mm
1.59 mm
1.6 mm
2.3 mm
3 mm
6 mm
9.5 mm
10 mm
13 mm
16 mm
19 mm
24 mm
25 mm
32 mm
38 mm
45 mm
48 mm
50 mm
54 mm
57 mm
60 mm
65 mm
75 mm
90 mm
95 mm
100 mm
115 mm
120 mm
125 mm
140 mm
150 mm
165 mm
175 mm
190 mm
200 mm
215 mm
225 mm
250 mm
290 mm
300 mm
325 mm
350 mm
1.52 mm
1.59 mm
2.29 mm
3.18 mm
6.35 mm
9.52 mm
12.7 mm
15.87 mm
19 mm
23.8 mm
25.4 mm
31.8 mm
38 mm
44.5 mm
50.8 mm
64 mm
76 mm
102 mm
152 mm
203 mm
229 mm
305 mm
37
Equivalent U.S.
Unit
0.031 in.
0.059 in.
0.063 in.
0.063 in.
0.091 in.
0.118 in.
0.24 in.
0.374 in.
0.394 in.
0.51 in.
0.63 in.
0.75 in.
0.945 in.
0.98 in.
1.26 in.
1.50 in.
1.77 in.
1.89 in.
1.97 in.
2.13 in.
2.24 in.
2.36 in.
2.56 in.
2.95 in.
3.54 in
3.74 in.
3.94 in.
4.53 in.
4.72 in.
4.92 in.
5.51 in.
5.91 in.
6.5 in.
6.89 in
7.48
7.87 in.
8.46 in.
8.86 in.
9.84 in.
11.42 in.
11.81 in.
12.8 in.
13.78 in.
15 in.
16 in.
17 in.
18 in.
19 in.
20 in.
22 in.
24 in.
26 in.
27 in.
30 in.
36 in.
38 in.
40 in.
42 in.
44 in.
54 in.
96 in.
1 ft
2 ft
2 ½ ft
3 ft
3.5 ft
4 ft
4 ½ ft
5 ft
5 ½ ft
6 ft
6 ft 6 in.
6 ½ ft
6 ft 7 in.
7 ft
7 ft 6 in.
8 ft
9 ft
10 ft
12 ft
14 ft
15 ft
16 ft
17 ft
18 ft
20 ft
21 ft
22 ft
25 ft
27 ft
30 ft
381 mm
406 mm
375 mm
400 mm
425 mm
450 mm
475 mm
500 mm
550 mm
600 mm
650 mm
675 mm
750 mm
900 mm
950 mm
1.0 m
1.0 m
1.1 m
1.4 m
2.5 m
300 mm
600 mm
750 mm
900 mm
1.0 m
1.2 m
1.4 m
1.5 m
1.7 m
1.8 m
2.0 m
2.0 m
2.0 m
2.1 m
2.3 m
2.5 m
2.7 m
3.0 m
3.7 m
4.3 m
4.5 m
4.9 m
5.2 m
5.5 m
6.0 m
6.4 m
6.7 m
7.5 m
8.0 m
9.0 m
457 mm
557 mm
610 mm
659 mm
762 mm
914 mm
1.02 m
1.07 m
2.44 m
305 mm
610 mm
762 mm
914 mm
1.07 m
1.22 m
1.37 m
1.52 m
1.68 m
1.83 m
1.98 m
2.0 m
2.13 m
2.29 m
2.44 m
2.74 m
3.05 m
3.66 m
4.27 m
4.57 m
4.88 m
5.2 m
5.49 m
6.1 m
6.4 m
6.7 m
7.62 m
8.23 m
9.14 m
38
14.76 in.
15.75 in.
16.73 in.
17.72 in.
18.7 in.
19.69 in.
21.65 in.
23.62 in.
25.59 in.
26.57 in.
29.53 in.
35.73 in.
37.40 in
39.37 in.
39.37 in.
43.30 in.
55.12 in.
98.43 in.
0.98 ft
1.97 ft
2.46 ft
2.95 ft
3.28 ft
3.94 ft
4.59 ft
4.92 ft
5.58 ft
5.91 ft
6.56 ft
6.56 ft
6.56 ft
6.89 ft
7.55 ft
8.20 ft
8.858 ft
9.84 ft
12.14 ft
14.11 ft
15.09 ft
16.08 ft
17.06 ft
18.05 ft
19.69 ft
20.997 ft
21.98 ft
24.61 ft
26.25 ft
29.53 ft
35 ft
40 ft
50 ft
60 ft
70 ft
75 ft
80 ft
100 ft
135 ft
140 ft
150 ft
200 ft
1000 ft
10.67 m
12.2 m
15.2 m
11 m
12 m
15 m
18 m
21 m
23 m
25 m
30 m
41 m
42 m
45 m
60 m
300 m
23 m
24.4 m
30.5 m
42.7 m
61 m
305 m
39
36.09 ft
39.37 ft
49.22 ft
59.06 ft
68.9 ft
75.46 ft
82 ft
98.43 ft
134.48 ft
137.76 ft
147.65 ft
196.86 ft
984.3 ft
INDEX
permissive, 3, 11, 12
physical damage, 9, 16, 25, 26, 32
purpose(s), 7, 8, 10, 14, 29, 33
references, 8, 11, 13, 19, 21, 22
responsibilities, 2, 3, 24
rules, 3, 12, 21, 23
scope(s), 3, 4, 8, 10
standard(s), 2, 3, 4, 11, 15, 17, 21, 27
subdivisions, 3, 5, 6, 8
tables, 3, 4, 5, 8, 9, 17, 19, 35
terms, 9, 11, 12, 13, 14, 15, 16, 19, 27,
36
unenforceable, 13, 14, 34
units of measurement, 4, 16, 17, 27, 28,
30, 34, 35, 36
vague., 13
voltage, 7, 15, 16, 29, 31, 34
word choices, 3, 13
word clarity, 19
writing style, 3, 17
abbreviations, 15
acronym, 15
annexes, 8
conversion, 17, 32
definitions, 9, 19
document structure, 3
editorial, 4, 23
exceptions, 11, 13, 25
extracted material, 17, 23
extracts, 3, 22
figures, 3, 9
guarding, 16, 30
guidelines, 4, 17
informational note(s), 4,11, 12, 13, 21,
23
language, 2, 12, 17, 18, 19, 25
mandatory, 3, 4, 9, 10, 11, 12, 13, 21
numbering, 4, 6, 7, 10
parallel construction, 20
parts, 5, 6, 9, 10, 16, 19, 21, 30
40